Linked Data Practices for the Geospatial Community

Transcription

1 Linked Data Practices for the Geospatial Community Talk subtitle Presented at GEOSS Workshop on Climate Boulder Colorado, 23 September 2011 Stephan Zednik, RPI / Tetherless World Constellation

2 Value Proposition of Linked Data Discover Web resources easy to generate and link to Access Leverage HTTP methods Integrate RDF is a standard mechanism for specifying the existence and meaning of connections between items described in the data Use Web standards for data access and representation simplify data consumption while providing (extreme) expressivity

3 Principles of Linked Data There are 4 principle expectations (rules) for Linked Data 1. Use URIs as names for things 2. Use HTTP URIs so that people can look up those names 3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL) 4. Include links to other URIs, so that they can discover more things

4 World Wide Web of Data!

5 Linked Data Languages SKOS (Simple Knowledge Organizational System) Thesauri, Taxonomies, Topical Hierarchies RDFS (RDF Schema) Vocabularies OWL (Web Ontology Language) Ontologies RDFS+ RDFS + Subset of OWL

6 Reuse Key factor in re-usability of data: structure Regular and structured is Easier to find Easier to make tools for More likely to be referenced and therefore beneficiary of network effect

7 Re-use Concerns Usage & Uptake Maintenance & Governance Coverage Expressivity Modularity

8 Example: SWEET 2 Dependency Graph astrobody_owl spaceobject_owl phys_owl physdynamics_owl chem_owl human_owl physdynamicsrotational_owl mathrelation_owl scisystemdynamics_owl math_owl spaceextent_owl sciresearch_owl top_owl sciunits_owl scisystemstate_owl mathvector_owl time_owl scimodel_owl physpressure_owl physenergy_owl sciordinal_owl scirole_owl scicategorical_owl scisystem_owl mathfunction_owl astrogeodesy_owl physelecmag_owl sciinstrument_owl spacedirection_owl spacerelation_owl astroplanet_owl physcontinuummechanics_owl spacedistribution_owl humancommerce_owl humanstructure_owl space_owl mathstatistics_owl chemstate_owl chemwater_owl chemcompound_owl physspectrum_owl astrohelio_owl physplasma_owl physwaves_owl physparticle_owl astrostar_owl astrosun_owl physthermo_owl phystransport_owl atmowind_owl chemconcentration_owl chemcharge_owl physradiation_owl physspectrumuv_owl chemcompoundhydrocarbon_owl chemelementalmolecule_owl chemelement_owl atmo_owl mathcalculus_owl atmoboundary_owl spacescale_owl physfluidinstability_owl atmofront_owl atmostability_owl atmothermo_owl physfluid_owl physfluiddynamics_owl atmowindmesoscale_owl landorographic_owl chemstatechange_owl mathsolution_owl timediurnal_owl atmocloud_owl physsolid_owl atmowave_owl atmopressure_owl atmofog_owl landcoastal_owl atmoprecip_owl hydrobodyofwater_owl landfluvial_owl physgravity_owl cryo_owl landlandform_owl physfluidwave_owl atmowindglobal_owl atmoearthreference_owl physradiationmedium_owl chemprocess_owl ocean_owl oceancirculation_owl atmolightning_owl physsound_owl timescale_owl atmosky_owl landsediment_owl biol_owl biolplant_owl hydro_owl geol_owl landgeomorphology_owl clim_owl geolmineral_owl atmowindscale_owl sciprovenance_owl timeextent_owl biolanimal_owl biolbiome_owl chemcompoundorganic_owl climzone_owl biolprocess_owl climindicator_owl timeseasonal_owl biolecology_owl biolhealth_owl biolmicrobiota_owl chemacidity_owl chemcompoundacid_owl chemcompoundcfc_owl chemcompoundhalon_owl chemcompoundion_owl chemisotope_owl climoscillation_owl envirassessment_owl envirimpact_owl envircontrol_owl humandecision_owl enviremissionsource_owl envirindicator_owl envirpollutant_owl envirprotection_owl humanjurisdiction_owl envirsustainability_owl envirregulation_owl envirstandards_owl envirtransport_owl geolpetrology_owl geolbasin_owl geolconstituent_owl physsolidconsistence_owl geolcontinental_owl geolpetrologyigneous_owl geoltectonics_owl geolorogen_owl physsoliddeformation_owl landtectonic_owl timegeologic_owl physsolidfailure_owl geolearthreference_owl geolearthquake_owl geolfault_owl geoloceanic_owl oceanice_owl geolresource_owl geolvolcano_owl humanagriculture_owl humancommunications_owl humanenergy_owl humanextraction_owl humantransport_owl humantransportair_owl humantransportspace_owl hydrogroundwater_owl hydrosurface_owl info_owl infofile_owl inforeduction_owl infoservice_owl infotechnology_owl landglacial_owl landsoil_owl landvolcanic_owl oceanearthreference_owl oceanfloor_owl physspectrumvisible_owl sciuncertainty_owl spacecategory_owl spacecoordinates_owl

9 Finding Vocabularies No current definitive directory to find existing vocabularies SchemaWeb, SchemaCache, Swoogle Statistics on usage of vocabularies in the wild Section 2.3 of the State of the LOD Cloud

10 Using Vocabularies If suitable terms are found, they should be re-used Maximizes potential for consumption Network effect on re-used vocabulary New terms should be mapped to wellestablished existing vocabularies Standards bodies useful to establish & promote vocabularies Network effect long-term driving factor Example: FOAF

11 W3C Geo Vocabulary Basic RDF vocabulary that provides a namespace for representing latitude, longitude, and other spatially located things using WGS84 as a reference datum Wide usage, but far too simple for GIS tools <rdf:rdf xmlns:rdf=" xmlns:geo=" <geo:point> <geo:lat>55.701</geo:lat> <geo:long>12.552</geo:long> </geo:point> </rdf:rdf>

12 OGC GeoSPARQL Includes RDF/OWL Vocabulary for representing spatial information A set of functions for spatial computations A set of query transformation Rules Expressivity for GIS tool requirements groups/geosparqlswg

13 OGC GeoSPARQL RDF

14 Discovering Linked Data Standard discovery of linked data is via other linked data OpenSearch Version 1.1 Geo extension (very basic) Semantics? DataCasting ProductCasting InventoryCasting ServiceCasting

15 Querying Linked Data SPARQL Endpoint Requires understanding of structure Generally domain agnostic Faceted Browsing Pelorus S2S workinggroups/s2s Supports Widgets

16 SPARQL Endpoint Web Browser

17 Pelorus

18 S2S Faceted Browser

19 Services & Linked Data SOAP Web Services and Linked Data are not complementary Document exchange vs Web of Data SOAP ignores HTTP access semantics REST (Representational State Transfer) HTTP as a mechanism for retrieval of resource representations exposed via URIs Resource Orientated Architecture (ROA) Stateless interactions Linked Data and RESTful services can be complementary Will take care in design

20 References Tom Heath and Christian Bizer (2011) Linked Data: Evolving the Web into a Global Data Space (1 st Edition) Synthesis Lectures on the Semantic Web: Theory and Technology, 1:1, Morgan & Claypool. DOI: /S00334ED1V01Y201102WBE001 GeoSPARQL SWG JPL Datacasting Pelorus S2S